These cuprite crystals are from the Milpillas Mine in Cuitaca, Mun de Santa Cruz, Sonora, Mexico. Mining at this locale began in 2006 with the extraction of copper minerals. Thirty-six mineral species have been identified at the mine including cuprite. It is a secondary mineral found in oxidized copper ore bodies and it contains the elements Cu, C and O. Mining started in several copper oxide zones where outstanding secondary copper mineral specimens were recovered. This specimen consists of a quartz matrix (sawed on the rear surface) that hosts an exposed vein that is filled with dozens of red cuprite crystals. The cuprites are complex and their luster is mirror like. This piece measures 3 x 1 3/4 x 3/4 inches or 76 x 46 x 19 mm.